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Index
AAccelerated testing and statistical lifetime
modelinglifetime tests
end-use, 391load profile effect, 393MEA/system, 392system variables, 391–392
mechanistic test, 390–391membrane electrode assemblies (MEAs),
385–386screening tests
catalyst, 388–389gas-diffusion layer, 389–390membrane, 386–388
SPLIDA data, 394–395standard deviation, 393–394statistical analysis, 393Weibull distribution, 395
AC impedance analysis. See Tafel slopeAciplex®, 134Air impurities
automotive applications, 290–291cathode compartment, 291contaminant propagation routes
accelerated tests, 296airstream components, 293bipolar plate, 292–293cathode compartment case, 297Donnan exclusion, 296elements, 291–292exposure scale, 296sources, 294–295system process flow diagram, 292testing protocols, 296unit cell design, 292–293
mathematical modelscatalyst layer level, 297flow-field channel, 297, 303
fluid ingress causes, 304, 306gas-diffusion layer, 303hydrophilic electrode, 304–305ionomer degradation effects, 304, 306ionomer dehydration, 305Langmuirian-based model, 307metallic bipolar plate, 304nafion hydrophilic channels, 304–305oxygen reduction pathway, 304performance losses types and
mechanisms, 298–302platinum dissolution rate, 304thermodynamic properties, 303
mitigation strategiescathode compartment, 308, 314kinetic and ohmic effects, 314material approaches, 308types, approaches, effects, and
mechanisms, 308–313Aoki, M., 62Azaroual, M., 10
BBakelite®, 162Base polymers, 135–136Baurmeister, J., 350Bett, J.A.S., 407Binder, H., 403Bindra, P., 10, 14Bipolar plate design
channel-based flow fieldsgas-diffusion layer (GDL), 421–423humidification system, 423–424
integrated air injection, 427–428interdigitated flow field, 424–425plate requirements, 420–421porous cathode/cooling plate, 426–427porous gas distribution structures, 425–426
497
498 Index
Borup, R., 10, 18Bradean, R., 436Butler–Volmer expression, 218
CCapillary flow porometry (CFP) data,
184–185CARBEL® CL substrate, 169, 170Carbon bipolar plates, 253–254Carbon black
applications, 29properties, 30
Carbon corrosion. See Start–stop degradationdurability
local anode hydrogen starvation, 50start/stop conditions, 49–50
general theory of, 15–16heterogeneous sessile-drop contact angles
modelingCassie equation, 178fluropolymers, surface coverage,
178, 179hydrophobicity, 179surface porosity, 179–180
kineticscarbon weight loss, 32, 34cell voltage loss, 35–36electrochemical oxidation, 30–31vs. corrosion rates, 33
in PEMFCs, 16–18RH sensitivity changes
constant-voltage current density, 183ex-situ aging effects, 183, 184GDLs vs. identical cells, 182hydrophobic interface, 183scanning, 182
surface chemistry and wettability changesLANL in-house goniometer, contact
angle measurement, 176surface energy measurement, 178Toray TGP-H GDL, Owens–Wendt
technique, 177X-ray photoelectron spectroscopy (XPS)
analysisdrive-cycling experiment, ELAT®
version 2.0, 180–181oxygen to carbon signal intensity ratio,
181–182Carbon oxidation reaction (COR) current, 38Carbon potential effect
electrochemical oxidation, 403energy-storage system, 405reverse-current mechanism, 404
Carbon-supported membrane electrode assemblies
in automotive operative conditionsglobal anode hydrogen starvation,
40–41local anode hydrogen starvation,
42–43start/stop conditions, 38–40steady-state conditions, 36–37transient conditions, 37–38
carbon blackapplications, 29properties, 30
carbon corrosion kineticscarbon weight loss, 32, 34cell voltage loss, 35–36electrochemical oxidation, 30–31vs. corrosion rates, 33
corrosion-resistant carbonBET surface normalized, 46electrochemical corrosion, 44–45gas-phase oxidation, 44graphitized and nongraphitized carbon
blacks, 45Cassie equation, 178Cathode degradation, 478–481Cathode electrocatalysts
platinum monolayerlong-term stability test, 19–20oxygen reduction reaction (ORR), 18
stabilizationaccelerated stability testing, 21catalytic activities, 21–22electronic effects, 22–23scanning tunneling microscope, 21X-ray absorption near-edge structure
measurement, 21–22CCD. See Charge-coupled-device cameraCell and stack operation
accelerated testing and statistical lifetime modeling
lifetime tests, 391–393mechanistic test, 390–391membrane electrode assemblies
(MEAs), 385–386screening tests, 386–390SPLIDA data, 394–395standard deviation, 393–394statistical analysis, 393Weibull distribution, 395
contaminants impactair impurities, 289–314electrode reactions, 323–337performance and durability, 341–361
Index 499499
freezingdynamics, 379–380ice formation and frost heave, 378–379material properties and morphology,
373–374mitigation strategies, 380–381performance degradation, 372–373requirements, 371–372water state, 374–377
technical level, 285Celtec® membranes, 200CFP. See Capillary flow porometry dataChang, P.A.C., 433Channel-based flow fields
gas-diffusion layer (GDL), 421–423humidification system, 423–424
Charge-coupled-device (CCD) camera, 191Chemical degradation, PFSA membranes
accelerated testing methodology, 62–63decomposition mechanism
hydrogen-containing end groups, 66hydroxy/hydroperoxy radicals, 65–66
durability, 66–67mechanism
diagnostic life testing, 59–60electron spin resonance (ESR) signals,
61–62H
2O
2 formation, 60–61
H2 permeability in current density, 59
Nafion®, 58open-circuit conditions, 63–64platinum-band formations, 64–65vs. physical degradation, 57
Chen, J., 141, 148Chen, Y.L., 141, 148Condensation, 411Contaminants impact
air impuritiesautomotive applications, 290–291cathode compartment, 291contaminant propagation routes,
291–297mathematical model, 297–306mitigation strategies, 308–314
electrode reactionsmembrane electrode assembly
(MEA), 323oxygen reduction reaction (ORR),
326–337rotating disk electrode (RDE), 324–326
performance and durabilityAB optimization process, 351–353anode overpotential measurement,
342–344
CO mitigation methods, 344–351crossover O
2 effect, 353–354
N2 dilution and inertial effect, 358–359
potential electrode-poisoning species, 359–361
reformate, 341–342transient CO effect, 354
Conway, B.E., 8CO tolerance decrease
Cole–Cole plot and Bode plot, 458–460limiting current density model, 457–458simulated reformed gas (SRG), 456–457
Crosslinked graft copolymer, 137Curtin, D.E., 66
DDarcy air permeability, 185, 186Degradation
cathode activity loss, surface oxide formation
methanol-oxidation electrocatalysis, 226oxide-layer growth process, 226–227six-cell DMFC stack, 226, 227
cathode degradation, 478–481cathode (oxygen reduction) kinetics
cyclic voltammetry measurements, 213oxygen reduction overpotentials,
212, 213cathode mass-transport overpotentials, 214dual-cell setup
cathode potential measurement, 206, 207
current flow measurement, 208H
2/air and air/H
2 fronts passage,
208–209reverse current cell, 207startup and shutdown situation, 209
electrochemical surface area loss (ECSA)sintering mechanisms, 231transmission electron microscope
images, DMFC catalysts, 231, 232electrode degradation modes, 204–205idling
disadvantages, 478operational phenomena, 476–477
load-cycling, 475–476low- vs. high-temperature PEFCs
cell voltage, 215, 216linear regression lines, 216
membrane degradation modes, 203–204membrane–electrode interface
electrode flooding, 235electrophoretic deposition process, 236
500 Index
Degradation (cont.)high-frequency resistance (HFR),
234, 235long-term performance, 233, 234Nafion®-bonded electrodes, 233polymer electrolyte membrane
(PEM), 236postmortem analysis, 234
Ohmic cell impedance, 211operating conditions, 469–470platinum nanoparticles
crystallite migration and coalescence, 13–14
dissolution and redeposition, 14precipitation, 15
ruthenium crossovercarbon monoxide stripping scan,
DMFC cathode, 228, 229cathode contamination, 230electrochemical treatment, 230, 231MEA fabrication process, 229–230nanocrystalline Pt–Ru alloy,
electrochemical oxidation, 228start/stop operation, 205–206start–stop operation
carbon oxidation, 471–472mitigation effect, 473–474operation, 470–471
underlying process, 214–215Del Popolo, M.G., 22Density–potential curve, 246Direct methanol fuel cell durability (DMFC)
“accelerated testing,” 225catalyst degradation
cathode activity loss, surface oxide formation, 226–228
electrochemical surface area loss, 230–232
ruthenium crossover, 228–230cathode catalyst oxidation, 237H
2–air fuel cells, 225
membrane–electrode interface degradationelectrode flooding, 235electrophoretic deposition process, 236high-frequency resistance (HFR), 234, 235long-term performance, 233, 234Nafion®-bonded electrodes, 233polymer electrolyte membrane
(PEM), 236postmortem analysis, 234
“required-power line,” 224stack performance degradation, 236–237steady-state performance, 225voltage loss, cell operation, 224
Durabilitycarbon-support corrosion
local anode hydrogen starvation, 50start/stop conditions, 49–50
for commercialization of PEFCs, 3perfluorinated polymer-based MEA
constant current durability, 127–129current–voltage curves of, 127degradation reactions, 131open circuit voltage (OCV) conditions,
126–127scanning electron microscope, 129–130
PFSA membranes, 66–67radiation-grafted membranes
base polymers, 135–136grafting monomers, 136–138membrane aging, 134membrane material properties,
141–144proton transport, 133
EECSA. See Electrochemical surface area lossElectrochemical carbon corrosion, 205Electrochemical Ostwald ripening, 14Electrochemical reactions
nonoptimal conditionsglobal anode hydrogen starvation,
40–41local anode hydrogen starvation, 42–43
optimal conditionsstart/stop conditions, 38–40steady-state conditions, 36–37transient conditions, 37–38
Electrochemical surface area (ECSA), 230–232, 453–454
Electrode potentialcarbon potential effect
electrochemical oxidation, 403energy-storage system, 405reverse-current mechanism, 404
oxygen-reduction reaction (ORR), 400–401
platinum electrode potential cycling, 402–403
Electrode reactions, fuel cellsmembrane electrode assembly (MEA), 323oxygen reduction reaction (ORR)
alkylammonium ion impurities, 328–330
impurity cations, 332–334metal cation impurities, 326–328methanol concentrations, 334–335
Index 501501
organic impurities, 330–332platinum surface, 336–337
rotating disk electrode (RDE)Nafion® polymer, 324–325organic impurities, 325Pt/Nafion® film analysis, 325pyridyl compounds, 325–326
Electrolyte membrane degradation. See Idling degradation
Electron spin resonance (ESR) spectramembrane chemical degradation, 100–101perfluorinated polymer-based MEA,
121–124relative humidity effects, 78–79
FFilter-press-type stacks, 431–432Flemion® membrane, 66, 150Freezing
dynamics, 379–380ice formation and frost heave, 378–379material properties and morphology,
373–374mitigation strategies, 380–381performance degradation, 372–373requirements, 371–372water state
cell models, 377gas-diffusion medium, 376–377liquid–solid phase, 374–375mass-transport characteristics, 375Nafion, 375porous-electrode theory, 377saturation levels vs. temperature, 376thermodynamic equilibrium, 374
Fuel cell stack, vehicle applicationdegradation phenomena
cathode degradation, 478–481idling, 476–478load-cycling, 475–476operating conditions, 469–470start–stop, 470–474
membrane electrode assembly (MEA) degradation, 467–469
Fuel cell testingessential improvements, 144–146grafting parameters, 146innovative monomer and crosslinker
combinations, 146–148postmortem degradation analysis,
151–152sample and testing, 148–151
Fuel processors, 200
GGalvanic cells, 432–433Gas-diffusion layer (GDL), 421–423
carbon corrosionCassie equation, 178fluropolymers, surface coverage,
178, 179hydrophobicity, 179RH sensitivity changes, 182–184surface chemistry and wettability
changes, 176–178surface porosity, 179–180X-ray photoelectron spectroscopy
(XPS) analysis, 180–182compression nonuniformity effects
electrical and thermal maldistribution effects, 190–191
mass-transport effects, 191–192substrate fiber puncturing,
membrane, 190conventional materials
Bakelite® usage, 162durability, 162heat treatment, 162–163pore size distribution (PSD)
properties, 163substrate raw-material fibers,
oxidation, 162hydrophobicity loss
durability testing, 171, 172fluoropolymer treatment, 172GDL and MEA chemical interaction,
165–166“GDL hydrophobicity gradient,” 172quick water-spraying experiment, 171resistivity trends vs. durability testing
time, 173, 174single cell polarization analysis,
172–173single-fiber contact angle, 166–169surface energy and dynamic contact
angle, 169–171“US06” drive-cycling testing, 173, 175
microporous layer coating (MPL), 160MPL degradation
carbon corrosion, 189material loss and air permeability,
184–186total and hydrophobic PSD changes,
186–189and MPL limitations, overview, 164MPL materials and GDL substrates
evaluation, 163–164scanning electron micrographs, 160, 161
502 Index
Gas diffusivity, 454–456Gaskets
material selectionadvantages, 277compression stress, 277, 279elastomers, 276–277R-class rubbers, 278silicone fragments (SiO
2), 279
mechanical requirementsflat design, 273, 275gas-diffusion layer, 276media resistance, 275membrane materials, 274sealing design concepts, 273–274stack components, 273
test methods, 280GDL. See Gas-diffusion layerg-PSSA membranes, 105–106Graft copolymerization, 138–141
advantages, 138ex situ properties, 140–141membrane-electrode interface, 140swollen membranes, 139
Grafting monomers, 136–138crosslinkers, 137α-methylstyrene (AMS), 138styrene monomers, 136
Groβ, A., 22Gruver, G.A., 406Guilminot, E., 15
HHe, S., 379Heterogeneous cell operation
galvanic cells, 432–433start/stop stochastic differences, 437start/stop systemic differences, 435–436stochastic differences, 436–437systemic differences, 433–435
High-frequency resistance (HFR), 234, 235High-temperature polymer electrolyte fuel
cellsfuel processors, 200high-temperature PBI membranes,
201–202individual overpotentials calculations
Butler–Volmer expression, 218fuel cell cathode, 217Tafel slope analysis, 217–218
membrane electrode assemblies (MEAs), 200
oxygen reduction reaction (ORR), 200proton conductivity mechanism, 200
start/stop cycling, 200typical degradation mechanisms
cathode (oxygen reduction) kinetics, 211–214
cathode mass-transport overpotentials, 214dual-cell setup, 206–209electrode degradation modes, 204–205low- vs. high-temperature PEFCs,
215–217membrane degradation modes,
203–204Ohmic cell impedance, 211start/stop operation, 205–206underlying process, 214–215
Hodgdon, R.B., 144Hommura, S., 63, 66Honji, A., 14Hubner, G., 130Humidification process, 413–414Humidity. See Humidification processHydrocarbon-based membranes, 58Hydrocarbon polymers, 104Hydrogen oxidation reaction (HOR), 42–43Hydrophobicity loss
cathode mass-transport overpotentialdurability testing, 171, 172fluoropolymer treatment, 172“GDL hydrophobicity gradient,” 172quick water-spraying experiment, 171resistivity trends vs. durability testing
time, 173, 174single cell polarization analysis,
172–173“US06” drive-cycling testing, 173, 175
composite surface energyCARBEL® CL substrate, 169, 170electrochemical impedance
spectroscopy measurements, 170sessile-drop contact-angle, 169, 170SIGRACET® GDL layer, 170, 171
GDL and MEA chemical interactioncathode degradation process, 166corrosion, 165
single-fiber contact angleaging environment, 168TGP-H paper, water droplet
penetration, 167–168Wilhelmy-plate technique, 166
IIdling degradation
disadvantages, 478operational phenomena, 476–477
Index 503503
Integrated air injection, 427–428Interdigitated flow field, 424–425
JJohnson, D.C., 12
KKangasniemi, K.H., 403Komanicky, V., 11Kulikovsky, A.A., 437
LLaConti, A.B., 60, 61, 63, 152LANL in-house goniometer, 176Load-cycling degradation, 475–476Localized membrane degradation
anode vs. cathode, 90–92inlets and edges, 94–95ionomer binder, 95–96platinum precipitation line, 92–94
Long-term durability tests, 460–463
MMader, J., 201Mathias, M.F., 16, 409Media manifolding, 428Membrane aging, 134Membrane chemical degradation
catalystcobalt, 89membrane durability tests, 88–89platinum, 88
characterization techniqueselectron spin resonance spectroscopy,
100–101energy dispersive X-ray (EDX)
spectroscopy, 102Fourier transfer IR (FTIR)
spectroscopy, 96–99nuclear magnetic resonance, 103–104Raman spectroscopy, 99–100X-ray photoelectron spectroscopy
(XPS), 102–103contamination effects
catalyst contamination, 87–88membrane contamination, 84–87
end-group stabilization, 110–111external load effects
electrochemical consumption, 76reactant gas depletion, 75
fluoride release rate (FRR), 72g-PSSA membranes, 105–106hydrocarbon membranes
chemical stability, 112long-term durability, 104–105
key elements for, 72–73localized degradation
anode vs. cathode, 90–92inlets and edges, 94–95ionomer binder, 95–96platinum precipitation line, 92–94
membrane thickness effects, 83–84mitigation strategies, 112–113operating temperature effects, 81–82PFSA membranes
chain scission mechanism, 107–108chain unzipping mechanism, 106–107side-group attack, 108
radical sources, 109–110reactant gas partial pressure effects, 79–81relative humidity effects
degradation rate vs. H2O
2 concentration,
77–78humidification, 76–77hydroxyl radicals, 79permeability, 77in situ electron spin resonance (ESR),
78–79two-electron reduction mechanism, 74
Membrane electrode assemblies (MEAs), 160, 200
accelerated testing and statistical lifetime modeling, 385–386
in automotive operative conditionsglobal anode hydrogen starvation,
40–41local anode hydrogen starvation, 42–43start/stop conditions, 38–40steady-state conditions, 36–37transient conditions, 37–38
carbon blackapplications, 29properties, 30
carbon corrosion kineticscarbon weight loss, 32, 34cell voltage loss, 35–36electrochemical oxidation, 30–31vs. corrosion rates, 33
corrosion-resistant carbonBET surface normalized, 46electrochemical corrosion, 44–45gas-phase oxidation, 44graphitized and nongraphitized carbon
blacks, 45
504 Index
Membrane electrode assemblies (MEAs) (cont.)
current–voltage curves, 450–451electrode reactions, 323perfluorinated polymer
degradation mechanism, 121–126durability, 126–131experimental descriptions, 120–121
platinum-containing electrode, 244stack durability degradation, 468–469
Mench, M., 379Metallic bipolar plates
base materialsdensity–potential curve, 246formability, 247high bulk conductivity, 245–246
degradation procedure, 247–248surface treatment and coating
ceramic coatings and prototypes, 251–252
corrosion-resistant stainless steels, 250–251
cost issues, 252–253vs. carbon bipolar plates, 253–254
α-Methylstyrene, 138Microporous layer coating (MPL)
degradationcarbon corrosion, 189material loss and air permeability
capillary flow porometry (CFP) measurements, 184–185
Darcy air permeability, 185, 186total and hydrophobic PSD changes
aging/durability testing, 187mercury and water (intrusion)
porosimetry, 187, 188Mitsushima, S., 10, 12
NNafion®, 59Nagy, Z., 10New Energy and Industrial Technology
Development Organization (NEDO)CO poisoning, 491–492road development
Fuel Cell Hydrogen Technology Development Road Map, 492–493
polymer electrolyte fuel cell system, 494–496
Newman, J., 377New polymer composites (NPLs), 67Nonfluorinated hydrocarbon polymer
membranes, 104
OOhma, A., 65Ohmic cell impedance, 211Operating temperatures, PEFC
carbon corrosion effect, 408–410perfluorosulfonic acid (PFSA) membrane
system, 405–406platinum sintering, 406–408
Organic impuritiesalcohol oxidation, 331characteristics, 330–331polarization curves, 330, 332
ORR. See Oxygen reduction reactionOwens–Wendt technique, 177Oxygen evolution reaction (OER), 38Oxygen reduction reaction (ORR), 40, 200,
400–401alkylammonium ion impurities
Nafion® film, 330noncontaminant condition, 328–329oxygen transport, 329–330platinum oxide formation, 328
impurity cationsoxygen transport, 334platinum–ionomer interface, 332polarization curves, 333polymer mass, 332–333Pt–ionomer interface, 333–334
metal cation impuritiesion-exchange processes, 327–328kinetic current, 326–327metal–polymer electrolyte, 328Pt–Nafion® electrodes, 326
methanol concentrations, 334–335organic impurities
alcohol oxidation, 331characteristics, 330–331polarization curves, 330, 332
platinum surface, 336–337
PPEM. See Polymer electrolyte membranePerfluorinated polymer-based MEA
degradation mechanismaccelerated degradation method,
124–125electron spin resonance (ESR) spectra,
121–124molecular weight distributions, 126radical species identification, 121
durabilityconstant current durability, 127–129current–voltage curves of, 127
Index 505505
degradation reactions, 131open circuit voltage (OCV) conditions,
126–127scanning electron microscope, 129–130
experimental descriptioncell performances, 120hydrogen peroxide formation, 120radical species, 120–121
Perfluorinated sulfonic acid (PFSA) membranes
accelerated testing methodology, 62–63decomposition
hydrogen-containing end groups, 66hydroxy/hydroperoxy radicals, 65–66
durability, 66–67mechanisms
diagnostic life testing, 59–60electron spin resonance (ESR) signals,
61–62H
2O
2 formation, 60–61
H2 permeability in current density, 59
Nafion®, 58membrane chemical degradation
chain scission mechanism, 107–108chain unzipping mechanism, 106–107side-group attack, 108
open-circuit conditions, 63–64platinum-band formations, 64–65vs. physical degradation, 57
Performance and durabilityAB optimization process
AB-FRR chart, 351, 353CO–air bleed endurance tests, 351–352CO reformate test, 353steps, 351
anode overpotential measurementair bleed (AB), 343current density (CD) region, 344polarization data, 342–343
CO2 and reverse WGS (RWGS) reaction
anode overpotential anode, 357electrode poison, 355PtRu and platinum electrode, 356RWGS reaction, 357–358
CO mitigation methodsAB methods, 346–347CO-tolerant electrode, 345–346current pulsing method, 348–349high temperature PEFC, 350–351poisoning effects, 344–345pulsed AB (PAB) technology, 347–348reconfigured anode, 349–350
crossover O2 effect, 353–354
N2 dilution and inertial effect, 358–359
potential electrode-poisoning speciesH
2S and small organic molecules, 361
NH3 effect, 359–361
reformate, 341–342transient CO effect, 354
Perry, M.L., 408Phosphoric acid evaporation rates, 203, 204Physical degradation, 57Pianca, M., 98, 104Platinum
electrode potential cycling, 402–403sintering, 406–408
Platinum dissolution. See Load-cycling degradation
bulk materialpotential–pH diagram, 8–9PtO growth mechanism, 9–10thermodynamic behavior, 8
equilibrium solubility, 10–11potential cycling conditions, 11–12
Platinum nanoparticles, degradationcrystallite migration and coalescence,
13–14dissolution and redeposition, 14precipitation, 15
Polybenzimidazole (PBI), 200Polymer-electrolyte fuel cells (PEFCs)
auto manufacturers and stack makers, 489–491
corrosion initiators influence, 248–250durability, 443–444electrode potential
carbon potential effect, 403–405oxygen-reduction reaction (ORR),
400–401platinum electrode potential cycling,
402–403filter-press-type stacks, 431–432heterogeneous cell operation
galvanic cells, 432–433start/stop stochastic differences, 437start/stop systemic differences,
435–436stochastic differences under operation,
436–437systemic differences under operation,
433–435humidity, 410–414long-term durability tests, 460–463membrane electrode assembly (MEA),
244–245metallic bipolar plates
base materials, 245–247degradation procedure, 247–248
506 Index
Polymer-electrolyte fuel cells (PEFCs) (cont.)surface treatment and coating, 250–253vs. carbon bipolar plates, 253–254
operating temperaturescarbon corrosion effect, 408–410perfluorosulfonic acid (PFSA)
membrane system, 405–406platinum sintering, 406–408
residential cogeneration systemCO tolerance derease, 456–460fuel processing system, 448–450gas diffusivity decrease, 454–456membrane electrode assemblies
(MEAs), 450–451Osaka Gas, 447–448
Tafel slope and AC impedance analysis, 451–454
Polymer electrolyte membrane (PEM), 236Pore size distribution (PSD), 163Porous cathode/cooling plate, 426–427Porous gas distribution structures, 425–426Pozio, A., 61Promislow, K., 437
RRadiation-grafted fuel cell membranes
base polymers, 135–136fuel cell testing
essential improvements, 144–146grafting parameters, 146innovative monomer and crosslinker
combinations, 146–148postmortem degradation analysis,
151–152sample and testing, 148–151
graft copolymerizationadvantages, 138ex situ properties, 140–141membrane-electrode interface, 140swollen membranes, 139
grafting monomerscrosslinkers, 137α-Methylstyrene (AMS), 138styrene monomers, 136
membrane aging, 134membrane material properties
proton conductivity, 142reactant permeability, 143–144tensile properties, 141water transport properties, 142–143
proton transport, 133Rand, D.A.J., 12
Reiser, C.A., 200Residential cogeneration system
CO tolerance dereaseCole–Cole plot and Bode plot, 458–460limiting current density model,
457–458simulated reformed gas (SRG),
456–457fuel processing system, 448–450gas diffusivity, 454–456membrane electrode assemblies (MEAs),
450–451Osaka Gas, 447–448Tafel slope and AC impedance analysis
current–voltage curves, 451–452electrochemical surface area (ECSA),
453–454Reverse-current mechanism, 404Reversible hydrogen electrode (RHE), 30, 244Roduner, E., 130Rotating disk electrode (RDE)
Nafion® polymer, 324–325organic impurities, 325Pt/Nafion® film analysis, 325pyridyl compounds, 325–326
Roudgar, A., 22
SSchaeffler diagram, 246Schmidt, T.J., 350Sealing function, gaskets
material selectionadvantages, 277compression stress, 277, 279elastomers, 276–277R-class rubbers, 278silicone fragments (SiO
2), 279
mechanical requirementsdesign concepts, 273–274flat design, 273, 275gas-diffusion layer, 276media resistance, 275membrane materials, 274stack components, 273
test methods, 280Shao-Horn, Y., 10, 13SIGRACET® GDL layer, 170, 171Simpson, S.F., 372Solid electrolyte, 134. See also Perfluorinated
sulfonic acid (PFSA) membranesSoto, H.J., 360Springer, T.E., 377
Index 507507
Stack-compression hardware, 428–429Start–stop degradation
carbon oxidation, 471–472mitigation effect, 473–474operation, 470–471
Statistical lifetime modelingSPLIDA data, 394–395standard deviation, 393–394statistical analysis, 393Weibull distribution, 395
Stochastic differences, heterogeneous cell
under operation, 436–437start/stop operation, 437
Styrene monomers, 136Subfreezing phenomena. See FreezingSystemic differences, heterogeneous
cellunder operation, 433–435start/stop operation, 435–436
TTafel slope
analysis, 217–218current–voltage curves, 451–452electrochemical surface area (ECSA),
453–454Thermal cycling process, 412
UUribe, F.A., 360
VVirkar, A.V., 14
WWang, G., 437Wang, X., 11Water-recovery devices, 411–412Weber, A.Z., 377Weibull distribution, 395Wetton, B., 437Wilhelmy-plate technique, 166Wilson, M.S., 372Woods, R., 12
XX-ray photoelectron spectroscopy (XPS)
analysisdrive-cycling experiment, 180–181gas-diffusion layer (GDL), 180–182membrane chemical degradation, 102–103oxygen to carbon signal intensity ratio,
181–182
YYou, H., 10
ZZhang, J., 10, 18Zhou, Y.K., 14
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